1. Field of the Invention
The present invention generally relates to a digital wireless transceiver apparatus, in particular, to a portable telephone device.
2. Description of the Related Art
FIG. 1 illustrates an external view of a conventional portable telephone device. The portable telephone device comprises a telephone unit 10 and a headset 20. The headset 20 may be optionally coupled to the unit 10. The unit 10 includes a telephone housing 11 and an antenna 12 that can be pulled out from the housing 11. A built-in earphone 13, a built-in microphone 14, operation keys 15, a display 16, and a transceiver section 17 that is hidden by the housing 11 are installed in the telephone unit 10. The housing 11 has a jack 18 for coupling the headset 20.
The headset 20 comprises a plug 21 for coupling with the jack 18, a headphone 22 corresponding to the earphone 13, a headset microphone 23 corresponding to the built-in microphone 14 and a paired cable 24 for connecting the headphone 22 and the headset microphone 23 to the unit 10.
Generally, portable telephones of this kind are designed for being used with an earphone 13 and a built-in microphone 14, being held in a hand, without using a headset 20. However, the telephones are designed for being used optionally with the headset 20 so as to avoid such a danger that the driver of a motor vehicle holds a telephone unit 10 while driving the vehicle.
When the headset 20 is to be used, the plug 21 should be inserted into the jack 18 of the telephone unit 10. The insertion causes the earphone 13 and the built-in microphone 14 to be disconnected from the transceiver section 17 while the headphone 22 and the headset microphone 23 are connected to the transceiver section 17, thereby enabling a use of the telephone unit 10 without holding it in a hand.
When, however, the headphone 22 is used for a digital portable telephone, a problem has been accounted, as follows. The conventional analog portable telephone transmits a radio wave with a constant amplitude during a telephone call. On the other hand, a digital portable telephone is adapted to sample an analog voice signal generated during a call is sampled with a fixed period of time for converting it into a digital signal. The thus resulted digital signal is temporarily stored in a buffer memory. The stored digital signal is spread with spread codes in a spread spectrum scheme and converted into a fast digital radio signal of, for example, 800 MHz for transmission through the antenna 12. In this instance, it is to be noted that the radio signal may be intermittently transmitted as a burst-mode signal under some conditions, for example, in the case of presence or absence of a voice signal to be transmitted or in the case of the line congestion.
When the headset 20 is connected the digital portable telephone, the radio wave of 800 MHz intermittently transmitted through the antenna 12 of the telephone unit 10 is caught by the cable 24 of the headset 20. The caught radio wave is interrupted with a low frequency component of, for example, several hundred Hz. to particular low frequency depends on a period of on/off control for the transmission of the radio wave. The burst signal may enter a voice amplifier in a receiver channel of the transceiver unit 17, or may be detected by the headphone 22, thereby causing noises with a frequency of several hundreds Hz in the headphone 22. Owing to the noise output from the headphone 22, the clarity of a caller voice will be significantly degraded. As such, there arises such a problem that the effective use of the headphone 22 is impaired.
It is an object of the present invention to provide a digital wireless transceiver such as a digital portable telephone device which is free from noises occurring in a headset that is connected thereto.
The foregoing and other problems are overcome and the object of the invention is realized by apparatus in accordance with the invention.
The present invention provides in a first aspect, a digital wireless transceiver apparatus having transmitting means for converting a voice signal into a digital signal to store the converted signal and f or modulating a carrier wave with spread spectrum codes of the stored signal, the transmitting means being operable f or transmitting the modulated signal in an intermittent mode; receiving means for receiving a spread radio signal for demodulating the received signal to obtain a voice signal; acoustic means for converting the voice signal into an acoustic sound; and transfer means for transferring the voice signal to the acoustic means through a cable; wherein the transfer means comprising: a first high-frequency eliminating means for preventing a high-frequency signal induced in the transfer means by the transmitted signal from arriving at the acoustic means.
Further, a digital wireless transceiver apparatus in a second aspect of the present invention is characterized by the transfer means further includes a second high-frequency eliminating means for preventing the high-frequency signal from arriving at the receiving means.
Still further, a digital wireless transceiver apparatus according to claim 2, wherein the transfer means includes a detachable coupler for relaying the voice signal between the receiving means and a paired cable interconnecting the coupler and the acoustic means, wherein the second high-frequency eliminating means being provided between the coupler and the paired cable.